POTTSVILLE (AP) — Four children and two adults were found dead in a house fire in eastern Pennsylvania early this morning and authorities were searching for the cause.

The blaze broke out around 11:55 p.m. Sunday at the single-family home in Pottsville. Firefighters later found the bodies inside, according to Schuylkill County emergency dispatch supervisor Bill Lindenmuth. The names and ages of the victims weren’t released.

The fire was declared under control shortly before 1 a.m. A Pennsylvania State Police fire marshal was at the scene this morning, but the cause of the blaze wasn’t immediately known.

Crews from all the city’s fire companies responded. Pottsville fire Chief Todd March said crews had to proceed carefully through the building because of the extensive amount of damage and firefighters were still pouring water on the home this morning.

Messages left with a state police investigator and the coroner’s office weren’t immediately returned.